1. Field of the Invention
The present invention relates to switchgears, and in particular, to switchgear suitable for multiple, parallel installation (hereinafter, referred to as side-by-side installation) of a vacuum-insulated switchgear to an existing air-insulated switchgear.
2. Description of Related Art
Power receiving facilities are provided with switchgears which include a circuit breaker for cutting off load current or accident current, a disconnecting switch and a grounding switch for ensuring workers' safety during load maintenance checks, a detector for detecting system voltage or current, a protective relay, and so on.
There are a wide variety of insulation methods for switchgears. In addition to a conventional air-insulated module and a cubicle-type gas-insulated switchgear (GIS) which uses SF6 gas as an insulating gas, switchgears of a solid insulation type, compressed-air insulation type, and total vacuum insulation type are being developed in recent years from a viewpoint of environmental responsiveness.
While each component, i.e., the breaker, disconnecting switch, and grounding switch, is being acceleratingly miniaturized by using the variety of insulation methods mentioned above, the following vacuum-insulated switchgear has been proposed, in which a double-break three-position vacuum-insulated switch having breaking and disconnecting functions and a vacuum-insulated grounding switch are combined into a single body by epoxy casting (for example, see Patent Document 1.)
The vacuum-insulated switchgear mentioned above has a unit inside its case, in which unit, a vacuum container containing the double-break three-position vacuum switch having breaking and disconnecting functions, and a vacuum container containing the switch having a grounding function are combined into a single body by epoxy casting. Being small, lightweight, and highly reliable, the vacuum-insulated switchgear can meet the requirements for smaller, lighter equipment in, for example, power distribution facilities in an urban region.
Furthermore, in recent years, user demands for power receiving facilities have become more diversified. For example, since every demand-site has different types of load and operating conditions depending on their purposes, each distribution system must be planned according to the user requirements considering system safety, reliability, operation maintenance, and future load addition. In this distribution system planning, the aspects of controlling a breaker, disconnecting switch, and grounding switch making up the power receiving facility as well as of monitoring and measuring voltage and current must also be taken into consideration.
In this case, the key point is how to reduce installation space for the above components and for various devices for controlling, monitoring, and measuring the components, to minimize investment cost for installation. Being small, lightweight, and highly reliable, the vacuum-insulated switchgear described above can flexibly meet various needs of the users.
In the distribution system planning, users may request new installation, additional installation, and/or relocation of a variety of switchgears. Especially for new installation of switchgears, not all switchgears in the substation can be newly installed at once due to a financial reason. This forces only a few switchgears to be installed at first. In this case, or in a case of additional installation of switchgears, the vacuum-insulated switchgears must be operated concurrently with existing air-insulated switchgears. In other words, the vacuum-insulated switchgears are to be phased in, replacing the existing air-insulated switchgears, as the recent vacuum-insulated switchgears, using a high insulation performance of vacuum, have been developed to be smaller than the air-insulated switchgears.
Here, the vacuum-insulated switchgear means a switchgear having switches such as a vacuum breaker, each placed individually in a plurality of units, are electrically connected by solid-insulated bus bars; and the air-insulated switchgear means a switchgear having switches such as a vacuum breaker, each placed in each unit, are electrically connected by air-insulated bus bars.
Patent Document 1: Japanese Patent Application Laid-open No. 2006-238522